Impregnating wood



Patented May 25, 1937 UNITED STATES PATENT OFFICE 1 IMPREGNATING woo Frank H. Lyons, Memphis, Tenn., assignor to E. L. Bruce 00., Mem of Delaware phis, Tenn, a corporation No Drawing. Application January 20, 1930, Serial No. 422,223. Renewed October 2, 1936 Claims.

' creosote. Zinc chloride, zinc meta-arsenite, Wolman salts and similar preservatives, must be applied to the wood in the form of an aqueous solution and according leave the treated lumber with a high moisture content. This necessitates a drying time of from three to six monthsbefore the lumber can be used for building operations. Pressure processes which are the kind that are in most common use necessitate the stocking of large quantities of lumber for satisfactory operation. One of the objects of my invention is to provide a process by which it is possible to achieve in a reasonable time, adequate penetration of the wood by a non-water preservative, without objectionable odor, using an open tank process. Moisture is held.in the wood in at least two different ways. One way is by absorption by the cell walls. Another'way is the holding oi. water mechanically on the cell walls 1. e. adsorption;

Under a standard condition of temperature and pressure, these two forms of moisture retention are in dynamic equilibrium 1. e. the adsorbed moisture is changing to absorbed moisture as fast as absorbed moisture is changing to adsorbed.

conditions by capillary attraction is, from a theoretical standpoint, difficult.

Increased penetration may be had by (1) the addition of a compound to the treat to make the capillary attraction more positive; (2) a preliminary treatment of the wood to make the capillary attraction more positive; and (3) evaporation of the moisture in the wood.

These ends are all attained by treating the wood by my method and with my composition in an open tank. The composition is heated by any suitable means to approximately 240 F. and maintained at this temperature. The wood is immersed in the bath and held there until it has reached practically the temperature of the bath and then it is transferred as quickly as possible to a second bath in which the same composition is at a temperature of approximately 140 F. In the hot bath, the moisture is largely driven out of the wood and the wood is expanded. when Penetration of an oil into the wood under these.

the wood is plunged into the cooler bath, the vacuum, which is created by the condensation of any water vapors in the wood, by the cooling of any air left in the wood, and by the capillary attraction, serves to draw the treat into the wood. 5 I

The preferred composition that I have discovered and found eflicient in use is as follows:

38-40 B. fuel oil gallons 480 l8-20 B. fuel oil ..do 480 10 Ortho-dichloro-benzol pounds 109 Beta naphthol do 350 These quantities will make up approximately 1000 gallons of treating solution.

The fuel oil acts as a solvent for the beta naph- 15 v thol which is a toxic material. The ortho-dichloro-benzol increases the penetration of the toxic bearing oil. Other solvents than fuel oil could be employed such as solvent naphtha, benzol, carbon tetrachloride, etc. Other organic 20 toxicmaterials than beta naphthol could be used such as di-nitro-chloro-benzene. Other penetration accelerators than ortho-dichloro-benzene can be used such as para-dichloro-benzene. 25

About 5% of beta naphthol is soluble in the aforesaid composition at 140 F. but at F. 50% of the beta-naphthol crystallizes out of solution. For a substance to be toxic, it must be at least. slightly soluble in water. Beta naphthol is sol- 30 uble to the extent of one pound to every thousand pounds of water. The presence of the betanaphthol in the precipitated form assures condi/ tions such that any water present can dissolve its full amount of beta-naphthol, the solubility 35 being low enough to insure a long period fof toxicity.

If the beta-naphthol, dissolved to saturation in cold oil, is injected into the wood, the solubility of the beta-naphtha} in water from this oil 30111.1 40 tion would be below the toxic strength desired to kill the fungi, but by using a hot saturated solution of beta-naphthol, there is deposited on cooling, as free crystals, about 50% of the betanaphthol on the fibers of the wood and this free 45 beta-naphthol is available for saturating any moisture in the wood to a strength much above that required for killing fungi. There is, therefore, available as a fungicide both the toxic dissolved in' the oil and the toxic which is present 50 as free toxic deposited on the fibers of the wood.

- B y myinvention I am able to impregnate wood orthe like by a novel method with a toxic substance, which thereafter. partially crystallizes along the cell walla-1 p I will be clear from the following example.

Six hundred and forty board feet of pine timbers 2 in. x 6 in. x 12 ft. weighing about 2,960 lbs. were stacked in a crate so as to allow a one inch space around each timber, and immersed ina tank containing the treating composition heated to 240 F. After remaining for 45 min., the load was removed from the hot tank and immediately submerged in the cold tank, which is kept at 140 F. by means of a steam coil. During the heating period in the hot tank the air in the wood is expanded and some of the moisture is evaporated. As the timbers cool in the cold tank, the air contracts and the water vapors condense and the treating composition is drawn in. Due to the particular composition of the treating solution,, more penetration is obtained by capillarity than with the fuel oil alone. The composition being used at 140 F. the 5% by weight of beta-naphthol is entirely in solution. After about 45 minutes the load is removed from the cool tank and weighed. As the lumber cools, the beta-naphthol crystallizes from solution until at F. one-half of the total amount has crystallized. The weight of the timber when taken from the cold tank was 3,210 lbs., about 250 lbs. of treating composition having been absorbed.

From the description, it will be seen, that I provide a toxic material which is soluble in organic solvents, and more soluble at the higher than the lower temperature. I am therefore, able to treat lumber with a solution of a toxic material at an elevated temperature, the solution being saturated at the final treating temperature with the toxic material, which on cooling, deposits the excess toxic on the fibers of the wood. In this way, I am able to impregnate wood without the use of water, with a toxic material which is present in the free state and in the solvents,- at the ordinary temperature of the wood.

While I have disclosed my invention in connection with the impregnating of wood, it is obvious that other porous materials could be similarly treated.

I claim:

l. The method of impregnating wood and the like to resist insect and fungi attack, with a solution containing as a toxicant, beta naphthol or the like in petroleum oil solvents, about 5% of the toxicant being soluble at about F. and 50% crystallizing out at about 70 F., comprising treating the wood with the hot solution to cause substantial impregnation of the wood therewith and lowering the temperature to cause crystallization of the toxicant onto the fibers of the wood.

The operating results of the process in practice 2. The method of impregnating wood and the like to resist insect and fungi attack, with a solution containing as a toxicant about 5% of betanaphthol or the like dissolved in petroleum fuel oils at about 140 F., comprising treating the wood with the hot solution to cause substantial impregnation of the wood therewith and loweringv the temperature to cause crystallization of the toxicant onto the fibers of the wood, about 50% of the toxicant crystallizing out onto the wood at 70 F., the amount of toxicant precipitated being sumcient to dissolve in any aqueous medium present to a concentration above that required to inhibit the growth of fungi and insect attack.

3. The method of impregnating wood and the like to resist insect and fungi attack, with a solu tion containing beta-naphthol or the like in a petroleum oil solvent made up of a mixture of equal parts of 38-40 B. and l8-20 B. fuel oils, about 5% of the toxicant being soluble in the oil mixture at about 140 F. and 50% crystallizing out at about 70 F., comprising treating the wood with the hot solution to cause substantial pregnation of the wood therewith and lowering the temperature to cause crystallization of the toxicant onto the fibers of the wood, the amount of toxicant precipitated being sufficient to dissolve in any aqueous medium present to a concentration above that required to inhibit the growth of fungi and insect attack.

'4. The method of impregnating wood or the like to resist insect and fungi attack with a solution containing as a toxicant, beta-naphthol or the like in a non-volatile oil solvent comprising treating the wood with said solution at an elevated temperature to cause substantial impregnation of the wood with the solution and lowering the temperature to about 70 F. to cause crystallization of apart of the toxicant onto the fibers of the wood, the amount of toxicant dissolved in the said oil at the elevated temperature and the solubility of the toxicant in said oil at the lower temperature being such that the amount of toxicant precipitated is sui'ficient to dissolve in any aqueous medium present to a concentration above thatv required to inhibit the growth of fungi and insect attack.

5. A wood article of manufacture impregnated with crystallized beta-naphthol and beta-naphthol in a non-volatile oil solvent, the amount of crystallized beta-naphthol being sufficient to dissolve in any aqueous medium present to a concentration above that required to inhibit the growth of fungi and insect attack.

FRANK H. LYONS. 

